Electric bedcover control with adjustable switch



May 17, 1966 R. 1 WRAY, JR 3,251,973

ELECTRIC BEDCOVER CONTROL WITH ADJUSTABLE SWITCH Filed April l5, 1964 C] my 44 M07 *i F|G.I gi/45- u,

FIG. 3

INVENTOR. Joe/Z L. Wray Jn BY a J9 (yafwweq ATTOR Y United States Patent O 3,251,973 ELECTRIC BEDCVER CONTROL WITH ADJUSTABLE SWITCH Robert L. Wray, Jr., Asheboro, N.C., assigner to General Electric Company, a corporation of New York Filed Apr. 15, 1964, Ser. No. 360,042 8 Claims. (Cl. 20o-122) This invention relates to electric bedcover controls and in particular to such controls which are adjustable by the user to select a bedcover temperature which is automatically maintained despite variations in the temperature of the ambient air.

Electric bedcovers are commonly provided with a manually adjustable means for controlling the proportion of time that the heating element `of the bedcover is energized in order to select the average operating temperature of the bedcover. As the temperature of the ambient air in the bedroom of the user is subject to considerable variation, it is desirable to provide such a control which is automatically responsive to the ambient air temperature to vary the periods of on -time of the bedcover. Conveniently, the ambient air responsive means is located in a bedside control unit which is somewhat removed from the electric bedcover. Thus, to insure accurate bedcover control, it is also necessary to incorporate in the control some device which simulates the temperature of the bedcover.

It is an object of this invention to provide an adjustable electric bedcover control responsive -to `ambient air temperature of simplied construction and having greater sensitivity to temperature changes and improved reliability.

It is another object of this invention to provide such a bedcover control having a compact construction and being adapted for assembly calibration and incorporation as a unit with other components into an electric bedcover control.

In carrying out the objects of this invention in one form thereof, I provide a housing having a xed contact and magnet assembly mounted on one end thereof. A bimetal blade is secured at the opposite end of thehousing and has a contact and magnetic means mounted on its free end adjacent the xed contact. A manually rotatable actuator engages a bearing surface on the bimetal blade, between the ends thereof. Upon rotation of the actuator, the position of the bimetal blade is varied with respect to the xed contact so that the user may vary the temperature at which it is desired to operate the blanket. The bimetal blade is responsive to the ambient temperature so that the free end of the blade deects toward the xed contact upon a decrease in ambient temperature. When the magnetic attraction between the magnet and the magnetic means is suiiicient, the blade is deflected around its medially engaged actuator to close the control contacts. To simulate the response of the control to the temperature of the blanket, a wire heating element is positioned in spaced relation to the blade in circuit with the control contacts and the blanket heater. When the control contacts close, the hea-ting element ybecomes heated and tends to cause the bimetal blade to -deec-t away from the fixed contact, providing an opposing force to the magnetic attraction. The use of the magnet insures a snap-action of the contacts, thereby eliminating chatter and arcing and the medially propped blade may be of minimal thickness to permit high sensitivity. An indicator knob is adjustably engageable with the rotatable ac-tuator and adapted for convenient calibration of the control.

Further objects and advantages of my invention may best be understood by reference to the following description taken in connection with the accompanying drawings in which:

FIG. 1 is a sectional view of the control taken on line 1 1 of FIG. 3;

FIG. 2 is a top view of a portion of the control with the dial removed for clarity;

FIG. 3 is a bottom view of the control, and

FIG. 4 is a schematic diagram showing the elements of the control connected in an electric bedcover circuit.

FIGS. 1-3 show an electric bedcover control having a generally rectangular housing 10 of insulated material, such as plastic. Housing 10 includes a pair of opposing end walls 11 and 12, side walls 13 and 14 and an upper wall 15 having apertures 16 and 17 formed therein. A pair of laterally extending integral flanges 18 and 19, having apertures 18a and 19a respectively formed therein, provide means for securing the control housing as a unit in a bedside control assembly (not shown).

An integral cylindrical projection 21 from upper wall 15, having an elongated recess 22 across the top of it, accommodates an assembly 23 which includes a magnet 24, a rivet or contact 25, and a terminal 26. Magnet 24 is fastened within a cylindrical chamber 27 of housing 10 by rivet 25. A reduced central portion 25a of the rivet extends centrally through magnet 24, aperture 16 and terminal 26. The lower end of rivet 25 provides an enlarged contact portion 25b and the upper end of rivet 25 is rolled downwardly to clamp magnet 24 and terminal 26 to housing 10.

Magnet 24 is a generally cylindrical block and preferably consists of a fine-particle, permanent magnet, material such as Lodex. A lower central recess 24a of the magnet encloses enlarged contact portion 25b of rivet 25. Rive-t 25 is preferably formed of silver and is dimensioned so that enlarged portion 25b has its lower surface in approximately the same plane as the lower surface of magnet 24.

Terminal 26 comprises an elongated strip of electrically conductive, resilient material having a width substantially the same as the width of recess 22 so as to prevent rotation of the terminal. For electrical connection to the bedcover circuit, terminal 26 is bent downwardly at one end and provides an aperture 28 for an electrical connection. As bestv seen in FIG. 2, terminal 26 bridges aperture 16 and is supported by spaced portions of the horizontal surfaces 21a on either side of aperture 16. To insure rm mounting of the magnet to the housing, the portion of terminal strip 26 which bridges aperture 16 is bowed slightly downwardly (when viewed as in FIG. 1) when secured so a-s to become part of assembly 23. Thus, the tendency of the terminal '26 to resume its normal, unbowed, form provides an upward bias on the undersurface of the upper rolled end of the rivet. This bias draws magnet 24 upwardly into firm engagement with the housing. Such lirm mounting is maintained even though rivet 25 may be slightly loose. The resiliency of terminal 26 also provides resiliency in the support of the magnet in housing 10.

A thermo-responsive bimetal element or blade 29, having a high expansion side 29a and a low expansion side 29]?, is secured in cantilevered fashion between a clamp or pad 30 and upper wall 15 of the control housing by a pair of suitable fastening means 31 and 32. In order to permit small incremental movements of blade 29, the surfaces of pad 3i? which contact the blade must be completely free from irregularities, such as burrs, which might cause binding of the blade. This may be adequately accomplished when, as is preferred,.pad 30 is of metal, by relieving the edges of the top surface of the pad. Bimetal blade 29 is relatively thin, being approximately .010 inch in thickness, and extends across the length of 3 housing 10 so that .its free end is juxtaposed assembly 23. High expansion side 29a of the bimetal blade is a 22% nickel stainless steel while low expansion side 29b is of Invar having 36% nickel and the lbalance iron.

For cooperation with magnet 24 and rive-t 25, a disk or target 33 of magnetic material is moun-ted on the free end of bimetal blade 219 by a second contact or rivet 34. As shownin FIG. 1, the assembly 23 Aand magnetic disk 33 with rivet 34 are axially aligned about the rivet axes so that when the free end of bimetal blade 29 is drawn toward assembly 23 by the magnetic attraction between magnet 24 and magnetic disk 33, the contacts 25 and 34 will be closed. As a contact portion 34a of rivet 34 eX- tends above the surface of target 33 the contacts will engage before the magnetic elements do.

In accordance with my invention, manually rotatable means are provided, including a shaft 35 and a dial 36 for varying the position of bimetal blade 29 with respect t assembly 23. Shaft 35 is cylindrical, extends throughl aperture 17 in housing 10 generally perpendicular to the upper wall of the housing, and is journaled by the circular wall lwhich defines aperture 17. An enlarged portion 37, at the lower end of the shaft, is positioned within a recess 38 in the upper Wall of housing 10. A shoulder 37a of enlarged portion 37 prevents the removal of the shaft upwardly from housing 10, and a spring washer 39 of suitable form, which at least partially surrounds a reduced portion 40 of shaft 35, permits only limited downward movement of the shaft.

Extending upwardly from the top surface vof shaft 35 are a pair of spaced integrally formed, resilient ears or projections 41 and 42.' The ears each include a hook portion having a horizontal shoulder to permit engagement between shaft 35 and dial 36. i

Dial 36 includes a sleeve portion 43 and a knob portion 44 which are preferably integrally formed. An annular shoulder 45 is formed within sleeve 43 to provide means lfor securely engaging shaft 35 and dial 36. It can be seen that as the dial is pressed downwardly onto shaft 35, the inner surface of sleeve 43 deects resilient ears inwardly until shoulder 45 has passed over the ears. The

the position shown in FIG. 1. Shoulder 43 is then positioned, vertically, between the ear hooks and the top surface of shaft 35. This relationship prevents relative vertical movement between shaft 35 and dial 36.

Rotative engagement between shaft 35 and dial 36, as well as adjustability of their relative rotative positions,

are provided by the cooperation of the splined inner surface of dial sleeve 43 with a splined portion 46 of shaft 35. External access to ears 41 and 42 is closed with a button 47 which provides a tubular projection 48. Projection 48 is dimensioned to t closely between ears 41 and 42 thereby insuring engagement between the hooked portions of the ears and shoulder 45. The knob portion 44 of dial 36 is suitably marked to indicate relative tem perature settings.

In accordance with this invention a face cam 50 is formed on the lower -surface of shaft enlargement 37 for engagement with a bearing surface or projection of limited area on bimetal blade 29. Preferably, the bearing surface is provided, as shown in FIG. 1, by a frustoconical rivet 51 which projects upwardly from blade 29 and extends through the blade to be secured thereto in rivet fashion. It can be seen that upon the turning of dial 36 by knob 44, the engagement of face cam 50 with projection 51 varies the position of blade 29 by exing the blade about its fixed end.

To control the energization of the lbedcover circuit with respect to the bedcover temperature, a wire heater 52 is arranged beneath the bimetal blade across the length of housing 10. The heater is secured to pad 30 and a terminal 53 at points 54 and 55, respectively, in any suitable rnanner such as welding. It has been found that a hooked portions of the ears then snap outwardly taking straight single piece wire of high resistance material such as Nichrome is ideal for accurate sensitivity of t-he control.

Terminal 53 is secured by a fastener 56 across the side walls 13 and 14 of the control housing and is positioned suiciently low in the housing so as to prevent engagement with blade 29 when the blade is in its lowermost position. Terminal 53 additionally provides a limit for the deflection of blade 29 downwardly should the control unit be subjected to impact such asits being dropped. A horizontally extending end portion 57 of terminal 53 provides an aperture 58 for electrical connection in the bedcover circuit.

FIG. 4 shows schematically the electrical connection of the control of FIGS. 1-3 in a bedcover circuit having a resistance heating element 59. The terminal ends 66 and 61 of the bedcover heating element are respectively connected to terminals 26 and 53 of the control with 120 volt line power applied between points 53 and 61 so that contacts 25 and 34 as well as bimetal blade 29 and heater 52 are serially connected tothe bedcover heating element 59 The control operates in the following manner. Assuming that knob 44 has been turned to the desired temperature setting and that contacts 25 and 34 remain open, a decrease in room temperature will effect a deflection of the free end of blade 29 toward assembly 23. When the magnetic attraction between magnet'24 and disk 33 is sufficient, i.e., when the magnetic elements are in vsufficient proximity to one another, blade 29 will deflect with a snap-action around the fulcrum provided by projection 51 and face cam 50. This action will close contacts 25 and 34 while maintaining the magnetic elements in magnetically attracted, slightly spaced relation. The closing of the control contacts energizes the bedcover heating element through bimetal 29 and heating element 52.

As the temperature of heater 52 rises with the continuous flow of current therethrough, bimetal blade 29 is heated at a given rate by radiation and convection. As the high expansion side 29a of blade 29 is away from element 52, the blade tends to bend away from assembly 23 and towards element 52. After a period of energization, the `bending force induced in blade 29 by the magnetic attraction between the magnet elements is less than the bending force induced by the temperature of heater 52 so as to snap the control contacts apart thereby turning the bedcover olf. In a minute or two, however, bimetal blade 29 cools as there is no current in heater 52 and disk 33 moves closer to magnet 24 with the upward deection of blade 29. At some point, the magnetic force of attraction again becomes greater than the restraining force of the blade and the disk 33 snaps toward the magnet 34 closing the control contacts. Thus, another heating cycle 1s initiated.

It should be noted that the position of blade 29is also varied in response to the ambient room temperature. Thus, as the room temperature increases, bimetal blade 29 will cool less rapidly reducing the on time of the bedcover circuit. Also, `by turning knob 44 counterclockw1se toward the LO position the user manually forces the magnetic disk 33 farther away from magnet 24 thereby requiring a lower ambient temperature to deflect the free end of blade 29 toward assembly 23. Of course as the knob is turned clockwise toward the HI position, face cam 50 permits blade 29 to rise to its normal horizontal position so that the magnetic Velements are closer together, thereby insuring a greater period of bedcover energization and consequent higher temperature.

As one aspect of my invention the bedcover control is designed for easy factory calibration. The calibration is conducted prior to the securing of dial 36 to shaft 35 as follows. In a temperature controlled room of approximately 72 F., with the control contacts held together magnetically, shaft 35 is turned just enough to force the free end of blade 29 away from its attracted position with 35 in the manner suggested above with the medial portion of the indicated temperature range aligned with an indicator marker (not shown) on the housing or on the bedside control unit in which the control is placed. The control is now calibrated. Should the user desire a temperature above that of the control calibration room, he has merely to turn the knob 49 toward the high position thereby raising the blade 29 so as to permit the magnetic attraction between the magnetic elements to close the control contacts. Should the user want a lower temperature he has merely to turn the knob toward the LO position and the bedcover will not be energized until the ambient temperature is cool enough to cause blade 2.9 to deflect to the contact position. In addition to providing means for the convenient accurate calibration of the control, the dial and shaft engagement insures an essentially tamper proof calibration of these elements. As is evident from FIG. l, button 47 prevents the users access to the engaging portions of shaft 35 and dial 36 or release of the dial from the shaft without special tools.

Of course, should any re-calibration be necessary, this may be accomplished as follows. Button 47 is pried out of engagement with the upper recessed surface of knob 44 and ears 41 and 42 are pressed toward one lanother by a suitable tool. The dial 36 may then be drawn upwardly for removal from shaft 35 and replacement at the desired calibration.

I have thus provided a control for an electrically heated bedcover which is responsive to both the ambient room temperature and to the temperature of the bedcover and which may be manually adjusted by the user to vary the temperature which is held in the bedcover. It should be particularly noted that the propped cantilever arrangement, whereby the face cam 50 provides a medial support for bimetal blade 29, permits the use of a relatively thin blade. Thus high temperature sensitivity is realized while still utilizing a himetal blade of substantial length. The unitary shaft-face cam arrangement also eliminates any necessity for a threaded engagement between the shaft and the control housing thereby greatly simplifying manufacture. Furthermore, the magnetic contact arrangement insures a snap-action of the control to reduce arcing and pitting to thereby give llong life to the control. It can be seen that the arrangement of shaft 35 with dial 36 also provides a very simple and highly accurate means for Calibrating the control Without resorting to threaded engagements.

While I have thus shown and described a specific embodiment of my invention, I do not desire my invention to be limited to the particular construction shown and described. Instead, I intend by the appended claims to cover all modifications within the spirit and scope of my invention.

What I claim is:

1. A device for controlling an electrically heated bedcover responsive to manual selection and ambient air temperature comprising:

(a) a housing;

(b) a thermostatic switch within said housing includ- (aa) a fixed contact, and (bb) a bimetallic blade secured to said housing at one end and having a movable contact on its free end adapted to engage said xed contact;

(c) means defining a bearing surface on one side of said blade intermediate its ends;

(d) manually rotatable means including a shaft having a longitudinal axis substantially perpendicular to the side of the said blade having a bearing surface, one end of said shaft having a face cam surface in cooperating engagement with said'bearing surface for varying deflection of said blade, said face cam surface providing a fulcrum intermediate the ends of said blade about which said blade is pivoted when said fixed contact engages said movable contact;

(e) a magnet positioned adjacent one of said contacts;

(f) magnetic means positioned adjacent the other of said contacts so that said contacts close with a snapaction when said magnet and said magnetic means are suiciently close to permit the magnetic force therebetween to deflect said blade over said face cam surface; and

(g) an electric heater positioned in proximity to said blade, said heater and said contacts being adapted for connection in circuit with the bedcover heating means, so that engagement of said contacts permits current to flow through said heater to heat the blade, thereby providing a defiecting force in opposition to said magnetic force.

2. The device as set forth in claim 1 wherein said magnet is secured to said housing.

3. The device as set forth in claim 1 wherein said bearing surface comprises a projection secured to said bimetallic blade and extends above the surface thereof.

4. The device as set forth in claim 1 wherein said magnet is generally cup shaped and is secured against said housing by a rivet and a resilient terminal strip.

5. A device for controlling an electrically heated bedcover responsive to manual adjustment by the user and the ambient air temperature, comprising:

(a) a housingof insulated material having an aperture extending between inner and outer surfaces thereof;

(b) a magnetic contact and terminal assembly including:

(aa) 'amagnet,

(bb) means defining an aperture in said magnet,

(cc) a resilient terminal strip engaging said housing at spaced points on opposite sides of said housing aperture on the outer Surface of said housing, with an intermediate portion adapted to be bowed for connection to said magnet to bias said magnet against the inner surface of said housing, and

(dd) a contact rivet extending through said magnet and said strip for resiliently securing said magnet to said housing and providing a contact portion adjacent said magnet:

(c) a thermo-responsive element secured to one end of said housing extending across the length of. said housing and arranged for transverse deflection in response to a change in temperature;

(d) magnetic means including a contact secured to the free end of said thermo-responsive element adjacent said assembly for closing said contacts with a snap-action when said magnet and said magnetic means are in sufficient proximity for the magnet force therebetween to detlect the free end of said thermo-responsive element toward said assembly;

(e) means deiining a bearing surface on said thermoresponsive element intermediate its ends;

(f) manually rotatable means in cooperating engagement with said bearing surface for deflecting said thermo-responsive element and for varying the distance between said contacts; and

(g) an electric heater adapted for connection in a circuit with the heating means of the said cover to supply heat to deflect said element away from said assembly whenever said contacts are closed.

6. A device for controlling an electrically heated bedcover responsive to manual selection and ambient air temperature comprising:

(a) a housing;

(b) a thermostatic switch within said housing includ- (aa) a fixed contact, and (bb) a bimetallic blade secured to said housing at one end and having a movable contact on its free end;

(c) means defining a bearing surface on one side of said blade intermediate its ends;

(d) manually rotatable means for varying the deflection of said blade including:

(aa) a shaft journaled in said housing,

(bb) an indicator dial having a sleeve portion adapted for rotative engagement with said shaft;

(cc) means including a pair of resilient hooked ears adjacent one end of said shaft for engagement with said dial to prevent axial movement between said dial and said shaft,

(dd) means on the other end of said shaft for cooperating engagement with said bearing surface for varying the deilection of said blade;

(e) a magnet positioned adjacent to one of said contacts; and n (f) magnet means positioned adjacent to the other of said contacts so that said contacts close with a snapaction when said magnetic means are sufficiently close to permit the magnetic force therebetween to deflect said blade over said bearingy surface;

(g) an electric heater positioned in proximity to said blade, said heater and said contacts being adapted for connection in circuit with the bedcover heating means, so that engagement of said contacts permits current to ilow through said heater to heat the blade, thereby providing a deiiecting force in opposition to said magnetic force.

7. The bedcover controlling device recited in claim 6 additionally including means adapted to be positioned between said ears to prevent disengagement of said shaft and said dial.

8. A device for controlling an electrically heated bedcover in response to manual selection by the user and the ambient air temperature, comprising:

(a) a plastic housing having opposing first and sec-v ond end walls;

(b) an assembly including a magnet, a first contact, and a iirst terminal secured to said housing adjacent said first end wall;

(c) a bimetallic blade extending across the length of said housing between said end walls, secured at one end of said housing adjacent said second end wall, and arranged for deflection in response to a change in temperature;

(d) a magnetic washer secured to the free end of said blade by a second contact, said washer and said second contact being poistioned on the surface of said blade adjacent said assembly and generally aligned with said magnet and said iirst contact, so

8 that said contacts are engaged with a snap action of said blade when said washer is in suiiicient proximity to said magnet to deflect lsaid blade by magnetic force; (e) means providing a bearing surface of limited area comprising an upstanding projection secured to said one surface of said blade intermediate its ends; (f) a rotatable face cam in cooperating engagement with said projection for adjusting the distance between said Washer and said magnet, said face cam surface providing a fulcrum about which said blade l pivots when said contacts are engaged;

(g) a shaft for said face cam journaled in said housing, said shaft having a longitudinal axis substantially perpendicular to the surface of said blade having a bearing ysurface and providing a pair of axially extending ears at the end remote from said face cam;

(h) a dial adjustably interlocking with said shaft ears and providing means for indicating the setting Which the user may select for the heating means of the bedcover;land

(i) a straight Wire electric heater electrically connected to the fixed end of said blade at one end and secured to a second terminal at the other end and positioned in spaced relation to the surface of said blade opposite said one surface, said terminals being connected in circuit with the heating means of the bedcover so that the engagement of said contacts causes current to flow through said heater to heat said blade and thereby deect said blade, and the magnetic washer carried thereby, away from said magnet.

References Cited by the Examiner UNITED STATES PATENTS 1,085,543 1/1914 Collins 287-53 2,413,100 12/1946 Crise 20G-138 2,523,041 9/1950 McKenzie 287-53 2,592,989 4/1952 Wilson 200-139 X 2,984,722 5/1961 Smith et al. 200-122 FOREIGN PATENTS 864,949 4/ 1961 Great Britain.

BERNARD A. GILHEANY, Primary Examiner. L. A. WRIGHT, Assistant Examiner. 

1. A DEVICE FOR CONTROLLING AN ELECTRICALLY HEATED BEDCOVER RESPONSIVE TO MANUAL SELECTION AND AMBIENT AIR TEMPERATURE COMPRISING: (A) A HOUSING; (B) A THERMOSTATIC SWITCH WITHIN SAID HOUSING INCLUDING: (AA) A FIXED CONTACT, AND (BB) A BIMETALLIC BLADE SECURED TO SAID HOUSING AT ONE END AND HAVING A MOVABLE CONTACT ON ITS FREE END ADAPTED TO ENGAGE SAID FIXED CONTACT; (C) MEANS DEFINING A BEARING SURFACE ON ONE SIDE OF SAID BLADE INTERMEDIATE ITS ENDS; (D) MANUALLY ROTATABLE MEANS INCLUDING A SHAFT HAVING A LONGITUDINAL AXIS SUBSTANTIALY PERPENDICULAR TO THE SIDE OF THE SAID BLADE HAVING A BEARING SURFACE, ONE END OF SAID SHAFT HAVING A FACE CAM SURFACE IN COOPERATING ENGAGEMENT WITH SAID BEARING SURFACE FOR VARYING DEFLECTION OF SAID BLADE, SAID FACE CAM SURFACE PROVIDING A FULCRUM INTERMEDIATE THE ENDS OF SAID BLADE ABOUT WHICH SAID BLADE IS PIVOTED WHEN SAID FIXED CONTACT ENGAGES SAID MOVABLE CONTACT; (E) A MAGNET POSITIONED ADJACENT ONE OF SAID CONTACTS; (F) MAGNETIC MEANS POSITIONED ADJACENT THE OTHER OF SAID CONTACTS SO THAT SAID CONTACTS CLOSE WITH A SNAPACTION WHEN SAID MAGNET AND SAID MAGNETIC MEANS ARE SUFFICIENTLY CLOSE TO PERMIT THE MAGNETIC FORCE THEREBETWEEN TO DEFLECT SAID BLADE OVER SAID FACE CAM SURFACE; AND (G) AN ELECTRIC HEATER POSITIONED IN PROXIMITY TO SAID BLADE, SAID HEATER AND SAID CONTACTS BEING ADAPTED FOR CONNECTION IN CIRCUIT WITH THE BEDCOVER HEATING MEANS, SO THAT ENGAGEMENT OF SAID CONTACTS PERMITS CURRENT TO FLOW THROUGH SAID HEATER TO HEAT THE BLADE, THEREBY PROVIDING A DEFLECTING FORCE IN OPPOSITION TO SAID MAGNETIC FORCE. 